1. Field of the Application
The present application relates to the field of electromagnetic valves. More precisely, the present application relates to a ball-type electromagnetic valve for controlling a fuel feed, in particular for a propellant feed in a space aircraft.
2. Description of Related Art
A rocket is propelled with the aid of a fuel (propellant), which is contained in on-board tanks. To supply the engines in a precise manner, solenoid valves are associated with the tanks. These valves generally have electromagnetic actuators utilizing the current from the electrical network of the rocket, the actuators having to adapt to the available voltage and intensity.
In order to hold open an electromagnetic valve, it is necessary to energize the coil thereof continuously. However, the current circulating here heats the temperature of the valve as a result, in some cases up to 100° C., which may cause the fuel to ignite. It goes without saying that this situation is to be avoided at all costs.
The fuel is propellant circulating in gaseous form at a temperature reaching −200° C. and a pressure of approximately 400 bar. This pressure exerts significant forces on the seal elements, as do the vibrations of a rocket during take-off. These vibrations may lead to accelerations of 60 g, which speed up the wear of the seal surfaces together with the impacts of closing movements. In the case of a ball cooperating with a seat, the closing movement generally causes the seat to absorb the kinetic energy of the plunger of the electromagnetic valve. For balls of reduced size, this leads to work-hardening of the seat and to a flattening of the ball tappet. During closing cycles the tappet does not move the ball sufficiently away from its seat, and the desired flow is not available in the absence of sufficient passage section. In addition, the degradation of the seat reduces the nominal tightness. It is therefore of interest to propose a valve with a ball that is pushed from its seat from the corresponding orifice.
Document DE 102007010213 B3 presents a valve to be actuated electromagnetically. The valve comprises a primary seat closed by a seal, which is in turn provided with a secondary seat to balance the pressures during opening. This secondary seat is closed with the aid of a ball which is held closed by a spring and which is opened thanks to a needle pushed by the plunger housed in the solenoid. The opening movement of the ball is performed through the seat, which makes it possible to prevent the ball from grinding against its seat during closure thereof. In this configuration the only kinetic energy absorbed by the seat is that of the ball and of the spring. However, this valve has an abrupt actuation of the ball. In addition, the elongate form of the valve exposes it in particular to vibrations on account of the inertia of the suspended portions
Although great strides have been made in the area of electromagnetic valves, many shortcomings remain.